This invention relates to rail mounting systems for electronic devices. More specifically, for DIN (Duetsche-Industrie-Norm) and NEMA (National Electrical Manufacturers Association) rail mounting systems.
These rail mounting systems are commonly used to support a variety of terminals, switches, relays, and can also support circuit boards by way of a mounting adapter. These rails are commonly longitudinally elongated, rigid, metal rails that are screw-attached to a base, like an inside surface of an enclosed cabinet. Different types of rails are defined by their dimensions and shape. These rails have standard and consistent dimensions invariable between manufacturers.
There are three prior art rails that my invention specifically relates/mounts to. These are DIN standard #EN 50035 (32 mm.), DIN standard #EN 50022 (35/7.5 mm.), and {22.4 mm.times.6.9 mm symmetrical NEMA A Series rails or DIN standard EN50045}. Examples of these rails can be seen in perspective view in FIG. 1 as notation 15, notation 16, and notation 17a, and 17b respectively. These rails can also be seen in FIG. 5 (notation 15), FIG. 6 (notation 16), and FIG. 7 (notation 17a) respectively. For easier understanding, these parts can be called: `G`, `wide-hat`, and `small-hat` respectively. Though 22.4 mm.times.6.9 mm symmetrical NEMA A Series rails are slightly wider than DIN standard EN50045, the means for attaching to them is substantially equivalent in this text.
Other examples of these rails can be seen on p. 90 in the DIN Rail Electronic Modules catalog of LMI Connectors, Inc., 1181 S. Rogers Cir. #30, Boca Raton, Fla. 33487. Their part numbers EN 50 035 32 mm and EN 50 022 35/7.5 mm are examples of `G` and `wide-hat` respectively. Other examples of these rails can be seen on sales sheets 8-87 and 8-88 by Allen-Bradley Co., 1201 South Second Street, Milwaukee, Wis. 53204. Their part numbers 1492-DR2, (1492-DR5 and 199-DR1), and (1492-N1, 1492-N22, and 1492-DR3) are examples of `G`, `wide-hat`, and `small hat` respectively.
In FIG. 1 an example of the orientation of all parts defined, shows 54 as a latitudinal edge, 53 as a longitudinal edge, and 55 as a transverse edge.
Common rails have transverse folds that can be called lips. The `G` rail's lips face medially. The lips of the `small-hat` and `wide-hat` rails face peripherally. These lips provide a surface for a mount to fixedly attach.
Prior art rail circuit board mounts include that of Module Shells Series 991100.00 Extruded PVC on the same page of LMI Connectors, Inc. catalog. The "Locking Feet" part, that mounts to a variety of rails, is a molded part that slides into an extruded "Module Shell". The molded part is rigid and longitudinally short. Molded parts are considerably more expensive to tool for and produce than extrusions. The Locking Feet's rigidity makes it difficult to snap onto a rail. This is because tabs, that must catch under the rail to hold it, must temporarily move transversely to accept the rail. Flexibility is most important for attaching the `G` and `small-hat` rails because of the narrow transverse distance between the lip's edges. The rigidity of the molded Locking Feet also makes it difficult to purposely remove from a rail. Molded Locking Feet are longitudinally stubby to increase the feet's flexibility to accept a rail. At least two Locking Feet are needed to longitudinally support any mounted circuit board. Assembly of the Locking feet to the Module Shell involves a pair of triple-screw molded end-plates, creating additional production expense.
Prior art rail mounts include DIN Rail Mount, shown on p. 107 of 310-55-20M catalog by Altech Corp., 35 Royal Road, Flemmington, N.J. 08822. Again it is a molded part that attaches to a selected rail. Again an extruded part supports a circuit board and is attached to the molded part. Again a multi-part assembly, including a molded part, is expensive. Again, at least two molded parts are needed to longitudinally support any mounted circuit board. The limited latitude (height) of the extruded part does allow for easy cutting to a desired longitudinal length.
Prior art rail mounts include SNAPTRACK.RTM. 2/8TKD, shown in FIG. 2, derived from Form #040-0267 REV 1, by Augat RDI, 525 Randy Road, Carol Stream, Ill. 60188. SNAPTRACK.RTM. 2/8TKD is a single extruded, longitudinally long track to mount on `G` and `wide-hat` rails. This track is not now commercially available. This SNAPTRACK.RTM. is an inexpensive extrusion mount. The mount's flexibility and latitudinal raise (between where the rail lips will be) appears to allow for easy rail mounting and removal. It appears latitudinally short, which would make it easy to cut to a desired longitudinal length.
But there are disadvantages to this SNAPTRACK.RTM.. Commonly-mounted relay circuits have several screw terminals on their transversely peripheral edges. Wires must be screwed to these terminals after mounting. The excessive SNAPTRACK.RTM. flexibility and lack of support on the transversely peripheral edges makes the screwing nearly impossible. This may be why it is not now being produced. Also this SNAPTRACK.RTM. only adapts to two rails.
Augat RDI currently sells TKAD DIN Rail Adapter and 6TK2D SNAPTRACK.RTM., shown in FIG. 3 (notations 52 and 51 respectively) derived from page 53 of 1995 catalog by Augat RDI. The TKAD DIN Rail Adapter is a semi-rigid molded part, making rail attachment difficult and rail removal nearly impossible, especially without a prying tool. The 6TK2D SNAPTRACK.RTM. extrusion is substantially flimsy. The Adapter is not transversely wide enough to support the extrusion's flimsy edges against the force of screwing to edge terminals on mounted circuit boards. The TKAD DIN Rail Adapter must be snapped into holes in extruded part 6TK2D SNAPTRACK.RTM.. This creates longitudinal track floppiness.